1. Field of the Invention
The present invention relates generally to an apparatus for checking pulse rate and heart rate independently by simply exchanging the heart sensor for the pulse sensor or vice versa, and more particularly to the apparatus with a heart sensor having a plurality of cone-shaped conductive rubber electrodes to differentially detect an electric cardiowave voltage signal generated from near the heart and a pulse sensor having a matching light-emitting diode and light-receiving phototransistor to detect the light reflected from the blood flowing through capillary vessels under the finger pad.
2. Description of the Prior Art
Recently, many people have taken an increasing interest in building up their physical strength or in promoting their own health, and therefore running has become more and more popular. However, in the case of a person developing his stamina or taking exercise who has no good adviser to coach him, the exerciser may be in danger of ruining his health due to excessively heavy exercise. To avoid such an unfavorable condition, there is an urgent need for a simple method of checking for a degree of exercise suitable to the user's current health conditions. One of the methods of checking the above-mentioned conditions is to check pulse rate or heart rate while the person is in motion.
The pulse rate is the number of blood surges in blood vessels generated whenever blood is fed from the heart to the blood vessels, that is, the number of pulses counted for one minute. A sensor for detecting the rate of pulse is usually attached to some portion of the body, preferably by selecting an appropriate skin site, such as fingertips or earlobes, where there are many capillary vessels under the skin.
For detecting the rate of pulse, a method has been adopted in which light is transmitted from a light emitting element to the capillary vessels near which the sensor is attached and the reflected light is next detected by a light-receiving element to detect the pulsatory motion of the blood.
In such a method as described above, however, there exists the factor of the weight of blood itself in addition to the pulsatory motion caused by the heart. When motion or vibration occurs within the body due to heavy exercise, this motion can cause the blood vessels to produce the same pulsatory motion as in the pulse, thus making it impossible to check the rate of pulse accurately when the person is in motion or in vigorous exercise.
In addition to the above problem, the blood vessels near the skin of the fingertips or earlobes are extremely sensitive to external temperature. When cooled the skin shrinks to prevent heat from being emitted; the blood vessels themselves also shrink to prevent heat from being transmitted; the blood vessels move away from the skin, thus making it impossible to detect the pulsatory motion of the blood reliably.
Furthermore, there is some difficulty in that when the body is exposed directly to the sun, direct rays of the sun are detected by the light-receiving element after passing through the skin, thus disturbing the accurate detection of the pulse rate, especially when a faint pulse rate is required to be checked.
Since there are many unstable factors when measuring the rate of pulse as already described hereinabove, there has been proposed a method of checking the number of heartbeats themselves, that is, the source of pulse.
The heart serves as a pump to feed blood throughout the body, and a kind of small current termed electrocardiowave passes through the heart whenever the heart beats. Therefore, the number of heartbeats is usually measured depending upon the number of these electrocardiowaves counted during one minute.
Since the electrocardiowave is not subject to the interfering influences of body vibration, change in external temperature, direct rays of the sun etc., it is possible to check the state of heartbeats more accurately. To detect such a small current as the cardiowave signal, however, it is necessary to attach the sensor near the heart, particularly in direct contact with the skin. Therefore, the person to be checked must be at least partially naked, which can be rather troublesome.
That is to say, since the described methods of measuring pulse rate and heart rate each have some merits and drawbacks, it is desirable to provide a simple single measuring unit which can check pulse rate or heart rate independently according to the time, place, and necessity, including the case of a person in motion.
In a conventional heart sensor, a plurality of electrodes are attached on the skin separately by using an adhesive tape, and connected to the measurement unit by using a plurality of long lead wires. Accordingly, it has been very troublesome to attach and detach the electrodes to and from the skin, and additionally there has been relatively great error caused by the positioning of the electrodes.
To overcome this problem, there exists a method of temporarily arranging the electrodes on a belt by using an adhesive tape. However, since the electrodes are simply arranged on a flexible belt and the lead wires are simply provided separately from the belt, the electrodes are liable to be moved while the person to be checked is in motion or engaged in exercise, thus producing unfavorable noise to interfere with accurate measurement of electrocardiowave signal.
Further, in the case of pulse sensors, there exist various kinds such as a simple sensor attached to the skin with adhesive tape, a clip-type sensor, a non-flexible plastic ring-shaped sensor, etc. However, these conventional sensors do not provide for easy attachment to the skin, elimination of perspiration, and comfort.